1. Field of the Invention
The present invention relates to human body communication, and more particularly, to a system and method for human body communication in which communication between a control device in contact with the human body and a mobile device positioned at a distance from the human body is performed using the human body as a transmission medium.
2. Description of Related Art
Generally, communication can be broadly broken down into two categories: wired communication using wire media, such as a cable; and wireless communication using wireless media, electromagnetic signals traveling through air or a vacuum. In addition to these, human body communication using the human body as a communication medium has recently been studied and products applying the results of this study using human body communication are being developed.
FIG. 1 is a schematic diagram illustrating a basic concept of human body communication.
Referring to FIG. 1, a control device 120 and a controlled device 130 are in contact with the human body 110 of a user. If the user applies a predetermined pressure or command signal to the control device 120, the control device 120 transfers the signal to the controlled device 130 through the human body 110. The controlled device 130 senses a flow of current through the body 110, and if it is determined that the sensed flow of current is caused by a control signal of the control device 120, performs an operation corresponding to the control signal.
Thus, the basic concept of human body communication is that communication is performed only when two different devices that want to communicate with each other are in contact with the human body. However, when necessary, one of the devices may be positioned (i.e., spacedly disposed) a predetermined distance from the human body 110. For example, when the user carries the controlled device 130 in a bag, the controlled device 130 put in the bag is positioned a predetermined distance from the user's body 110.
According to the conventional technology, considering that the controlled device 130 may be positioned a predetermined distance from the human body 110, the control device 120 transmits a signal with a high output power through the human body 110 so that the controlled device 130 can receive the signal from the control device 120 even if the controlled device 130 is positioned a predetermined distance from the human body 110. In this case, the high output power signal may have a detrimental effect on the human body 110. Also, since the high output signal is generated regardless of whether or not the controlled device 130 is in contact with the human body 110, so as to reach the controlled device in case it is not in contact with the body, the life of a battery used to drive the control device 120 is unnecessarily shortened. Furthermore, even though communication can be performed through transmission of a signal with minimum output power when the controlled device 130 is in contact with the human body 110, a high output power signal is still transmitted according to the conventional technology. As a result, communication is performed inefficiently.
Accordingly, there has been and continues to be a need to adjust the strength of an output signal transmitted from the control device 120 with respect to the distance between the controlled device 130 and the human body 110.